Rounding Continued - Problem fixed

[studio-n]

Ok, the frustration continues. I finally found an negative offset value that at least made it start at the right place (0.5") when the Z0 in the gcode said 0.5". but what I ended up with was a tapered dowel that ran from 1/2" to 3/4".
things only went downhill from there. So I started over with setting the left and right side up again (the tap off).
When I set the motor side, X, Y, and Z on the right side of the screen read 0,0,0. In reality, jogging the bit to the center point of the headstock (with the dead center point as the reference) it ended up at 0.255" from center. Ok, so I jogged it to the true center and set that to Z0.00. After setting the tailstock side, the mapped Z read 0.381". I jogged the bit over to the tail stock and it was in fact only about 0.065" from the headstock. This definitely accounts for the taper. Running the same rounding program the Z values ran from 0.507 (offset set to 0) to 0.672" on the tailstock side. that's 0.165" for a radius so only 0.33" NOT the 0.381" that the mapping indicates.
That wasn't the only strange stuff - sometimes I could enter a small offset, sometimes I couldn't. It would take a 2" offset but indicated anything less than 1" was too small. Sometimes it was the opposite. the same 2" was sometimes indicated as too large.

I haven't heard anything back from NWA other than I should update to SCP 2.1 build 14 which was the first thing we all needed to do to run the A-axis. Support is uneducated in the 4th Axis so they have to ask Tim and a mythical software engineer so no telling. So my original question still stands - "how is z0 calculated or set?". This is one buggy program so far. Anyone else having any success??

[Ronwoodson2]

Mine seems to work fine. I did two jobs of about 4 hrs each and there is very little variation from end to end in the z-axis.
I tap off on the chuck housing (chuck radius set to 1.75), then the tail stock housing with radius set to .625. Attached pic of
Future pencil cups show results. The other critical setting is Distance from tap off (motor end) to cutting area. This tells
Where along the material milling area begins.

[studio-n]

....I tap off on the chuck housing (chuck radius set to 1.75), then the tail stock housing with radius set to .625.

How did you determine the tail stock housing radius of 0.625? The width of it is 1" so my thought is that it would be half that. Or like I originally chose the dead center (0.5").
When you look at the xyz numbers under the "move to right" buttons, what is your Z value set to after the tap off? I wouldn't think it to be off as much as mine (0.311"). that large a drop over a
6" separation makes it look like my table is very crooked.

Did you have to set a z0? or just tap off and go. again, mine seems to be putting the actual z0 wherever it wants to. Cheers!
-Nick

[John Shaw]

I agree with the 1.75 if you tap off on the chuck body and .625 if you tap off on the flat top of the tail stock. These are the vertical distances from the tap off point to the work center line or spin axis. Also all tap off's need to be directly above the work/spin axis in order to get proper X,Y, spin axis alignment.
I would like to make a plea for Next Wave to publish some clear diagrams, and numbers for the furnished equipment in a stock setup - to get us started. As we use other chuck jaws etc, I realize some numbers may change and we will have to adjust.

[Ronwoodson2]

The key thing to remember is that on rounded stock Z0 is the center of the cylinder, and this is also considered the bottom of the 'unwrapped' model. So Z0 is the bottom
of the material, rather than the top as in normal CNC.
Z0 will be the center of the tailstock taper. Radius of the tailstock taper is .25 inches. Can't tap off there with material loaded, so I tap off on top of the housing,
which is .375 inches above the top of the taper. Adding these tells the machine I am tapping off .625 above the center of the taper. This is the value I enter as the radius of the tailstock chuck.
The software reads the elevation of the tap off point, subtracts the .625 value entered as the 'radius of tailstock chuck'
and sets Z0 as the center of the taper, or bottom of the unwrapped cylinder.
Z0 on the motor end is the center of the Midi chuck, or 1.75 inches below the top of the chuck housing.

Virtual Zero compensates for any irregularities in table flatness

This is how I see it all fitting together, and it seems to work for me. Hope it helps.

Ron

[studio-n]

Hello everyone, Yes the problem is solved. it was a misinterpretation of the instructions.
My tap off was on the body of the unit just behind the oil screw. That part of the housing is 4" diameter so the number entered should have been 2".
I was entering the actual diameter of the midi chuch which has a radius of 1.75". that accounted for the zero plane being lower than it should have.
After I manually zeroed the bit, it really threw off the tail stock end
since that is not changable. So now this run for a rounding job down to 0.5" came out at 0.5" on the headstock end and 0.51 on the tailstock end.

In testing this out I also learned that the offset must be a radius and not a diameter as the manual might lead you to belive. In one case, I set a rounding toolpath
to cut down to 0.35". It ended up at 0.45". I set the Lathe Cut Depth Offset to 0.1" and reran the job. What I ended up with was something 0.25" in diameter.
I reset that to 0.05" and when I ran the job for 0.5" I ended up at 0.5".

So thank you all for the advise and especially for NWA for helping out. Cheers!

Now that I can make it round it's time to start putting figures on it.